Contralateral Prophylactic Mastectomy Improves Survival Only Marginally in Patients with Unilateral Triple-Negative Breast Cancer: A Cohort Study Based on SEER Database

Background: The effect of contralateral prophylactic mastectomy (CPM) on the survival rate of triple-negative breast cancer (TNBC) patients is still controversial. The purpose of this study was to confirm whether unilateral TNBC patients benefit from CPM.Methods: 10006 patients with unilateral TNBC in the Surveillance, Epidemiology and End Results (SEER) database were enrolled in this study, propensity score matching (PSM) was applied to balance patient assignments. After PSM,3039 pairs of patients were divided into a CPM group and no-CPM group, respectively. All the patients have undergone total mastectomy or radical mastectomy. Cox proportional hazards regression models were used to evaluate overall survival (OS) and breast cancer-specific survival (BCSS) of the two groups. Subgroup analysis was introduced to exclude the effect of confounding factors. To identify potential variables for prognosis, Kaplan–Meier survival analysis and Cox regression analysis were used and were presented by Kaplan–Meier curve and forest plot separately.Results: With a median follow‐up time of 34.5months (IQR 1–83 months), the estimated 5-year BCSS rates for patients in the CPM group and the no-CPM group were 81.96% and 78.71%, the 5-year OS rates were 80.10% and 75.05%, respectively. CPM improved the BCSS (hazard ratio [HR]= 0.79; 95% confidence interval [CI]=0.69-0.90, p=0.001) and OS (HR= 0.74; 95% CI=0.66-0.84, p<0.001) of unilateral TNBC patients. Univariate subgroup analyses revealed that there was no significant difference in survival time for patients in stage N3 who underwent CPM or not (p>0.05).Conclusions: CPM only limitedly improved BCSS and OS in patients with unilateral TNBC undergoing total mastectomy or radical mastectomy and was not recommended for stage N3 patients.